Decline in quadriceps femoris muscle strength is common in individuals with knee osteoarthritis (OA),1 and is due primarily to disuse atrophy and impaired ability of the central nervous system to recruit existing motor units despite maximum conscious effort.2 In contrast to strength, muscle fatigue, which is defined as a temporary loss or decrease in force-generating ability due to recent contractions,3 has rarely been examined in patients with knee OA. Although methods to assess muscle fatigue in patients with knee OA have been validated,4,5 to the best of our knowledge, the only direct measure of muscle fatigue in this population was reported by Fisher et al.6 Their study of 15 male subjects (67.6 ± 6.1 years) with knee OA demonstrated that muscle strength and endurance were 50% lower than in an age-matched control group.
Muscle fatigue has important clinical implications due to the significant role of quadriceps muscle endurance for functional capabilities in the activities of daily living, such as walking and climbing stairs. As these capabilities are particularly affected in patients with knee OA,7 there is a need to expand our understanding of the characteristics of quadriceps muscle fatigue in this population.
The scope of the literature regarding quadriceps muscle performance in patients with knee pathologies has changed in recent years, shifting from a previous focus only